A typical automotive vehicle has a suspended portion, or body, such as a unit body or a frame supporting body work, which carries suspension attachment points. A suspension system supported on a ground engaging member (e.g. wheel) is attached to and supports the vehicle suspended portion at these attachment points. The configuration of available vehicle suspension systems varies widely.
One type of suspension system long used on trucks and passenger cars and still used on various off-road recreational vehicles, such as Jeep brand vehicles like the Jeep Wrangler, is illustrated in FIGS. 1A-1C. There a vehicle V has a suspended portion 111 which faces downward toward a prior suspension system PS. The latter includes a leaf spring 114 having a first end 117 which is pivoted on a first suspension attachment point 115 on the vehicle's suspended portion 111. A second end 116 of the leaf spring 114 is pivotally attached to a shackle 120. The shackle 120 in turn is pivotally attached to the suspended portion 111 at a second suspension attachment point 125. The attachment points 115 and 125 are typically spaced longitudinally along the vehicle. In the example shown, the vehicle suspended portion 111 is a body work supporting frame, and the suspension points 115 and 125 are pivot defining brackets pendant from and fixed to such frame. A mid-portion of the leaf spring 114 is fixed to a wheel supported axle 121, such as by a bracket 119, e.g. including U-bolts and a clamp plate as shown.
During vehicle travel on uneven ground, the leaf spring 114 flexes to allow the wheel to rise toward the vehicle body while rolling over a bump and to fall away from the vehicle body while rolling through a dip, i.e. the suspension system is respectively loaded and unloaded, such that the leaf spring respectively straightens and bows. The suspended portion 111 of the vehicle experiences a relatively level (i.e. relatively rise-free and fall-free) ride as the wheel rises and falls. To damp continued oscillatory flexing of the spring 114 after the wheel encounters a bump or a dip, and hence reduce continued oscillatory bouncing of the suspended portion 111 of the vehicle, it is conventional to interpose a damper between the axle 121 and the suspended portion 111 of the vehicle. Typically, the damper is a telescoping hydraulic shock absorber 110 which is fixed substantially vertically between the axle 121 and a third suspension attachment point 130 on the vehicle suspended portion 111. This third suspension attachment point 130 is located between the first and second attachment points 115 and 125 of the vehicle.
While traditional suspension systems, such as that illustrated in FIGS. 1A-1C, may perform adequately on the road or relatively smooth off-road terrain, applicant has found inadequacies in rougher off-road terrain.
For instance, as illustrated in FIGS. 1A-1C, a typical shock absorber 110 may have insufficient extension/retraction travel to allow the leaf spring 114 to fully flex and hence provide the maximum possible vertical wheel travel as the wheel rolls through severe bumps and dips.
Thus, the shock absorber 110 would have to be destroyed i.e. pulled apart or squashed as schematically shown in FIGS. 1A and 1C, respectively, to achieve the full bowing and straightening, respectively, of which the leaf spring is capable.
To increase wheel travel, the shock absorber 110 is sometimes removed. The spring can thus further bow and further straighten. However, upon sufficient additional straightening of the leaf spring, as illustrated in FIG. 1C, the shackle 120 may strike the vehicle suspended portion 111 and suddenly block further wheel/axle travel. The shock of one or more such events may break or otherwise damage the suspended portion 111 and/or parts of the suspension system.